1. Field of the Invention
The present invention relates to an assembly for placing a prosthetic valve in a lumen of the body, especially a heart valve, and in particular an aortic valve.
2. Background Art
Documents WO 91/17720, WO 98/29057 and EP 1 057 460 each describe an assembly, including the prosthetic valve to be implanted; a radially expandable framework, called a stent, which is able, in the expanded state, to bear against the wall of the body duct to be fitted with the valve, this bearing making it possible to immobilize this stent with respect to this wall; and means for fixing the valve to the stent. The placement of the stent permits mounting of the valve in the body duct, eliminating the need for an external access route and, thus, a direct surgical intervention.
However, major drawbacks of this technique are that it entails a risk of the valve being damaged by the balloon used to expand the stent, and it limits the force of expansion that can be imparted to the stent. This limitation has repercussions on the anchoring of the stent, making a displacement of said assembly possible. This limitation also has repercussions on the leaktightness of the stent in the area of the valvular ring which is particularly affected when calcified zones give the valvular ring an irregular form and/or a certain rigidity.
Another drawback of the prior art technique is that of directly joining the commissures of the valvules to the stent. The result of this is that an expansion of the stent, and thus of the valve, different than that intended may cause poor coaptation of the valvules and, consequently, defective functioning of the valve. The stent therefore has to undergo a predetermined expansion, which prevents or complicates adaptation of this stent to the anatomical variations.
In the case of implantation of an aortic valve, the prior art technique also has drawbacks in that it necessitates very exact positioning of the stent in the aorta so that the valve is located opposite the natural valvular ring, and it entails a risk of blocking the apertures of the coronary arteries that open out at the coronary ostia.